Let us discuss the procedure of entanglement swapping
in detail taking into account the quantum teleportation discussed in  Section IV-A. Quantum
teleportation is the transmission of quantum states stored in
specially prepared qubits which teleports the entirely
unknown quantum states, that are entangled to each other [1]}. Exploiting this circumstance, quantum repeater technology is realized. Supposing, quantum states are entangled between systems \(S_{1}\) , \(S_{2}\)  and between systems \(S_{3}\) , \(S_{4}\) . There is a probability of creating an entangled state between \(S_{1}\)  and \(S_{4}\) , by performing a joint Bell measurement on systems \(S_{2}\)  and \(S_{3}\) . The measurement result in terms of two classical bits, is sent to systems \(S_{1}\)  and \(S_{4}\)  through classical channels. Hence , entanglement between the end nodes \(S_{1}\)  and \(S_{4}\)  has been established even though entanglement was not possible due to long distance as they may never have interacted before. So, in this way this process can be repeated with multiple repeaters involved in entanglement swapping, extending over to larger distances.
Therefore, it can be seen that entanglement swapping is nothing but the quantum teleportation of entanglement of quantum states. Multiple teleportation procedures are performed by multiple repeater stations thus forming a quantum channel for transmission of quantum information between end nodes, that are thousands of kilometers apart physically.
